“If they were able to access that data point for home delivery and everything, it would open the door for more questions.”

A U.S. border officer who knew of a Canadian’s marijuana buying history could quickly put the person in an impossible position — admit to marijuana use and be banned as a “drug abuser,” or deny it and be banned for lying. (Immigration lawyers advise refusing to answer the question, which will probably get you turned back on that one occasion, but doesn’t carry lasting consequences.)

WATCH: Many British Columbians who travel south of the border may find themselves in legal limbo when Canada legalizes marijuana.

“Any information that goes outside of Canada is up for grabs by local law enforcement,” says Heather Black, a former assistant federal privacy commissioner. “It’s part of the globalization of data. It goes all over the place.”

“American authorities are pretty greedy for scooping up information, and they clearly don’t confine themselves to the borders of the United States.”

And under U.S. law, Canadians don’t have the safeguards over their U.S.-held data that Americans would have, explains University of Toronto law professor Lisa Austin.

“In Canada, we would be protected by the Charter. In the U.S. we’re not protected by the Fourth Amendment, as non-U.S. persons, so there’s no constitutional protection for our data.”

Mastercard, Visa and the CIBCdidn’t respond to questions about where credit card data is stored. However, the privacyagreements of all five of the bigbanks warn that customers’ financial data can be stored outside Canada, and be subject to the laws of the country it’s stored in.

Some don’t specify the U.S. by name, but others do. BMO’s agreement, for example, says that companies holding data “may be located outside of Canada (such as in the United States) and may be required to disclose information to courts, government authorities, regulators or law enforcement in accordance with applicable law in that country.”

WATCH: Public Safety Minister Ralph Goodale told the CBC that he believes banning Canadians from entering the U.S. for admitting to using marijuana is “ludicrous.”

In a 2005 decision, the federal privacy commissioner noted that Canadians’ credit card data held in the U.S. could be obtained by American authorities under the PATRIOT Act, an anti-terrorism law passed in the aftermath of the September 11, 2001, attacks.

At issue was a CIBC Visa cardholder agreement in which cardholders were asked to acknowledge that ” … my information may be processed and stored in the United States and that United States governments, courts or law enforcement or regulatory agencies may be able to obtain disclosure of my information through the laws of the United States.”

Under the law ” … certain U.S. intelligence and police surveillance and information collection tools have been expanded, and procedural hurdles for U.S. law enforcement agencies have been minimized. Under section 215 of the USA PATRIOT Act, the Federal Bureau of Investigation can access records held in the United States,” the decision said.

Research by B.C.’s Liquor Distribution Branch found that 15 per cent of the province’s adult population, or about half a million people, were interested in buying pot online, spokesperson Viviana Zanocco wrote in an email.

Global News contacted every province to ask where data about online marijuana customers — name, delivery address and so forth — will be stored:

Quebec,B.C., P.E.I. and Nova Scotia will operate their own online ordering systems directly, and plan to store the data only in Canada.

Alberta and Ontario have contracted out online ordering, but require the contractor to store the data only in Canada. Ontario won’t collect date of birth information through the ordering process, verifying age through an ID check at delivery instead.

Newfoundland and Labrador and New Brunswick haven’t chosen a contractor, but will impose a similar requirement.

Manitoba and Saskatchewan will allow online cannabis sales by licenced private-sector companies, and won’t limit where they store their consumer data. (Federal privacy laws have no requirement to keep data in Canada.)

Neither Manitoba nor Saskatchewan prepared privacy impact assessments about their approach to marijuana legalization, spokespeople for those provinces said. (A privacy impact assessment is a tool to try to make sure that something government does doesn’t affect privacy, or affects it as minimally as possible.)

They didn’t have to because the data will be handled by private-sector companies, they said.

WATCH: Public Safety Minister Ralph Goodale told the media Thursday that the federal government will intervene if border crossings into the U.S. become more difficult due to marijuana legalization.

Credit cards

Credit card data is a more challenging problem.

From the moment legal pot stores open, records of Canadians’ cannabis purchases are going to start to pile up in credit card data which the banks that issue the cards warn may end up south of the border.

So it’s an important question how credit card transactions will be recorded.

Nova Scotia cannabis purchases will be entered as NSLC (Nova Scotia Liquor Commission), which will make them effectively invisible in the data. Did the cardholder buy Bud or buds? It’s impossible to tell.

(“That’s smart,” Austin says. “It seems like the easiest way to solve the problem, to just not have the data available.”)

The credit card issue is “on our radar,” says New Brunswick Liquor Corporation spokesperson Mark Barbour. Nova Scotia’s cannabis sales will be run by a subsidiary of the NSLC, while New Brunswick’s will be run by a separate Crown corporation, Barbour points out. That makes it hard for New Brunswick to copy Nova Scotia’s solution.

WATCH: Donald Trump’s pick of an anti-pot U.S. attorney general has cannabis advocates on both sides of the border worried years of progress towards legalization will be rolled back. As Shirlee Engel reports, Jeff Sessions made no effort to calm these fears at his confirmation hearing.

In provinces with private-sector retailers, the details of credit card transactions are somewhat beyond government control. In Newfoundland and Labrador, for example, the name of the private-sector cannabis retailer will appear on the credit card statement, says liquor board spokesperson Greg Gill.

“The whole data piece, from domain name registration to credit card information, anything that might fall into federal U.S. hands, I can see how that would be a matter of concern, for sure,” he says.

At the U.S. border, enforcement is getting more intense

As attitudes toward marijuana have softened on both sides of the border, attitudes at the border itself have hardened, warns Len Saunders, an immigration lawyer in Blaine, Wash. Saunders is now seeing a flood of Canadian clients who want help with waivers related to marijuana after being banned for life by U.S. border officials.

“I see one or two cases a week now,” he says. “I used to see one or two a year. I’m almost seeing one a day, and that’s just me. It’s like a tidal wave of cases. I’ve never been so busy in my life doing waiver applications.”

Saunders says he has three Canadian clients, senior executives in an agricultural equipment company, who were banned for life when they tried to cross the border to do a sales demonstration of a marijuana bud trimming machine.

“All three admitted that they were selling this legal product to the marijuana industry. All were banned from the U.S. on the basis of reason to believe that they are involved in the drug trade. That’s how low the threshold is. They weren’t even involved with the product (the marijuana itself).”

WATCH: U.S. Customs has an early warning to Canadians in advance of any new pot laws. Paul Johnson reports.

Saunders and Railton both say they have no idea how U.S. border officials will react to legal marijuana in Canada.

“We really need the United States, and particularly the Department of Homeland Security, to issue a policy statement about how they’ll handle the fact that Canada legalizes,” Railton says.

Saunders recently appeared as a witness at Canada’s Senate national security and defence committee, which was holding hearings about border-related marijuana issues.

“Within a few days, I got an email from the U.S. embassy in Ottawa wanting me to discuss these issues with the embassy, because now the embassy is concerned about the thickening of the U.S. border,” he says.

“I’m sitting there thinking: ‘You guys are just discussing this now, when it’s almost legalized? It should have been discussed two or three years ago.’”

“I haven’t got a straight answer, or anything in writing, to give guidance when it does become legal in Canada, whether Americans are going to look at that favourably or not. You’d think that if it is legal in Canada it’s not going to create border crossing issues, but I’ve yet to have someone say ‘There’s no issue here.’ That’s the big question mark.”

WATCH: An immigration lawyer is casting serious doubt on some federal government advice to be honest and admit to smoking marijuana if asked at the U.S. border.